(1) Field of the Invention
The present invention relates to sarcosine or sarcosine compounds that are especially useful for anti corrosion of metal film in chemical mechanical polishing process. The composition enhances the anticorrosion ability of a work piece without leaving residues on the surface of a polished piece, or can protect the surface of a work piece from corrosion in post-CMP cleaning process.
(2) Description of Related Art
Due to continuous reduction in critical dimensions and rapidly increased number of the wiring layers of electronic components, the RC time delay has a significantly effect on the operation speed of entire circuits. In order to improve the problems of the time delay and the reliability of electron migration due to reduction in metal line width, copper conductor material with low resistivity and high resistance to damage by electron migration has been selected to replace aluminum alloys. However, because of the difficulty of etching copper, it is necessary to employ a damascene process in forming copper lines.
Damascene processes are different from traditional metallization processes, which initially define metallic patterns followed by filling trenches with dielectric layers. In the damascene process, a conductive line trench is first etched in a flat dielectric layer, filling a metal layer therein, and finally excess metal is removed to obtain a flat structure with metal inlayed in the dielectric layer. Damascene processes have the following advantages over traditional metallization processes: (1) the surface of a substrate is always kept flat; (2) the drawback that dielectric material is difficult to be filled into the spacing between metal lines in traditional processes can be eliminated; (3) the difficulty in etching metallic material, especially etching copper metal could be solved.
Further, in order to overcome the drawback that the necessity of separately fabricating a contact window structure and a metal conductor pattern leads to complicated fabrication procedures in traditional interconnection processes, a dual damascene process has been widely adopted in the industry. In the dual damascene process, line dielectrics and via dielectrics are etched off by selective etching twice, completing barrier layers of the metal layer and of the plug at a time, filling conductive metal into the vias and interconnection trenches at a time. With its low resistivity and high resistance to electron migration, copper has been gradually used as the material of interconnecting metal replacing aluminum to meet the demand of miniaturizing while enhancing operation speed of the components. Copper damascene interconnection technology not only can achieve the miniaturization of interconnects and the reduction of RC time delay, but also solves the difficulty in etching metallic copper. Therefore, it has become the main stream in the development of multiple interconnections today.
Regardless it is a single damascene or a dual damascene the copper process needs a planarization step to remove excess metal from the dielectric layer after completing the filling of copper. Chemical mechanical polishing process is the only one technique capable to achieve a global planarization. Copper CMP is usually carried out in two stages. In the first stage most copper is removed at a high removal rate to increase throughput of the process. In the second stage, the remaining copper is polished off at a low removal rate to prevent the copper in trenches from being excess polished. The two-stage copper polishing process usually needs to utilize different polishing compositions in order to achieve the requirements in the various stages.
In general, a chemical mechanical polishing of metal layers (copper) is conducted at pH value of weak acidic condition (different from that dielectric layers conducted under alkaline conditions) an addition of oxidant (e.g. hydrogen peroxide) is necessary to initiate passivation mechanism of metal therefore chemical removal occurs. However, unlike that aluminum would form self-protection oxide layers, copper metal is easily corroded and oxidized, so copper lines are frequently corroded and thus the quality of the interconnections is significantly impacted after polishing under such conditions.
To solve the above problem, a corrosion inhibitor such as 1H-benzotriazole (BTA) is added to prevent copper or alloys thereof from corrosion under acidic medium during polishing process. However, inhibitors such as benzotriazole would often leave residues on the surface of a work piece (a wafer) and they are difficult to be removed by cleaners such as high purity deionized water and the likes. The residue causes the surface of wafer become uneven and subsequent an extra annealing process is required.